Respostas bioquímicas e morfológicas de Tilápia-do-Nilo (Oreochromis niloticus) expostas ao material particulado atmosférico sedimentável oriundo de indústrias siderúrgicas

Abstract

The dust present in the atmosphere is called atmospheric particulate matter (MPA) and its composition depends on the emitting sources, which can be natural or anthropogenic. The emission and dispersion of pollutants are influenced by the wind and the size of particles present in the air. According to the size of the MPA, smaller and lighter particles can remain suspended, but depending on their constitution, these particles can aggregate more easily and form larger particles, called sedimentable MPA (MPASe). The blood alterations, responses of the antioxidant defense system and enzymes related to ionic regulation in the gills associated with possible histopathological changes which can alter the performance of the species in the face of other environmental challenges and compromise its survival were analyzed. Despite the high concentrations of Fe, Al,Ti, Mn and other trace metals in MPASe, the hematological parameters (RBC, Hct, [Hb], VCM, HCM and [HCM]) were unchanged, but some DNA instability indication in the erythrocytes was observed after exposure to 1 g.L-1 of MPASe for 96 hours. Regarding the immune system, the responses varied, with an increase in lymphocytes and a decrease in monocytes. The metals present in MPASe did not alter the functioning of the Na+/K+-ATPase enzyme in the gills and the plasma Na+/K+ balance was maintained however, the change in the plasma Na+/Cl- ratio with a decrease in chloride ion and in the activity of carbonic anhydrase enzyme at a concentration of 1 g.L-1 of MPASe indicate ionic unbalance. The antioxidant enzyme catalase in the gills increased activity for after fish exposure to 0.1 g.L-1 of MPASe; the activity of the biotransforming enzyme GST that acts in the conjugation of glutathione reduced (GSH) with xenobiotics increased in fish exposed to 0.1 g.L-1 of MPASe and the GSH content increased all groups exposed to MPASe. The oxidative stress biomarker LPO did not show significant differences for the gills, confirming that the metals present did not inhibit the performance of enzymatic and non-enzymatic antioxidant systems. In conclusion, the results of this study showed that the metals dissolved in the aquatic environment absorbed by the fish gills, although at sublethal level, caused genotoxic damage, change the immune system and antioxidants responses after 96 h-exposure. It could be harmful if animals are exposed for long periods as can occur in natural environment.